Rechargeable batteries have been used for many years in a variety of applications. In the past, nickel cadmium rechargeable batteries were used; however such batteries often have toxic effects and suffer from memory effects. For instance, if a nickel cadmium rechargeable battery is not fully drained before being recharged, the battery may lose its ability to be fully recharged. To avoid the negative features of nickel cadmium batteries, nickel metal hydride batteries are used for their additional storage capacity. In addition, nickel metal hydride batteries do not suffer from memory effects.
Rechargeable nickel metal hydride batteries carry a risk of overheating during recharging. This overheating may cause damage to the battery, the system in which the battery is used or the user. In order to avoid overheating, the temperature of the battery is monitored to ensure the battery does not overheat. A thermistor, or other temperature sensing device, is used to sense the temperature and often includes a shut off control when the temperature of the battery reaches a predetermined high point. The thermistor often requires the use of thermal epoxy or other thermal adhesives to conduct heat.
In existing thermal sensing systems (such as those discussed above), there may be limited contact between the thermistor or thermal contacts and the battery. For example, temperature is often sensed at the battery terminals. This can result in inaccurate temperature sensing.